1. Field of Invention
This invention relates to seatbelt systems and more particularly to seatbelt systems which fasten and unfasten the belt around the passenger of a motor vehicle.
2. Prior Art
Seatbelt systems use a passenger restraining belt to restrain and protect the passenger during vehicular emergencies. Such systems are arranged so that the passenger will not collide with dangerous objects during a vehicular emergency. However, the percentage of passengers who wear seatbelts is very low because of the difficulty in donning the belt, etc.
As a result, seatbelt systems have been proposed which make it possible to automatically fasten the passenger restraining belt around the passenger after the passenger has seated himself in the vehicle. In such seatbelt systems, a guide rail is fastened to the vehicle body and the movement of the runner piece is guided by the guide rail. An anchor plate which anchors the outer end of the belt is fastened to the runner piece. In this way, the belt can be caused to approach or move away from the passenger so that the belt is automatically fastened or unfastened from the passenger.
In such seatbelt systems, as in ordinary manually fastened seatbelt systems, it is necessary that the anchor plate be able to insure that the belt tension is securely supported by the motor vehicle body. Specifically, during an emergency such as a vehicle collision, the initial force of impact causes the passenger to apply a large tension to the belt. Accordingly, it is necessary to support this large tension securely with the vehicle body so that the restraint of the passenger is insured.
However in the case of anchor plates and runner pieces used in conventional automatically fastened seatbelt systems, there is the possibility that the runner piece will slip out of the guide rail when the belt tension is increased and incomplete restraint of the passenger will result.